Bump vitest from 2.1.8 to 2.1.9 in /webview-ui in the npm_and_yarn group

Bumps the npm_and_yarn group in /webview-ui with 1 update: [vitest](https://github.com/vitest-dev/vitest/tree/HEAD/packages/vitest).


Updates `vitest` from 2.1.8 to 2.1.9
- [Release notes](https://github.com/vitest-dev/vitest/releases)
- [Commits](https://github.com/vitest-dev/vitest/commits/v2.1.9/packages/vitest)

---
updated-dependencies:
- dependency-name: vitest
  dependency-type: direct:development
  dependency-group: npm_and_yarn
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]